As I understand it, Bootcamp is the dual boot solution while Parallels (And now VMWare) are the virtualization products...so using bootcamp would not necessarily require extra memory to function (Outside of Windows being a memory hog

)
As an interesting foot note, We have 2 iMacs in our lab running Windows XP exclusively...no OSX partition. You have to pre-partition the drive using the OSX setup disk. Make the whole thing NTFS and then boot off of the XP CD to setup up. Use the Bootcamp driver CD once it is all done and you have an OSX-less Mac. Why you would want one is another story
http://www.parallels.com/landingpage...FRGsGgodDGX7og
http://www.vmware.com/beta/fusion/
http://www.apple.com/macosx/bootcamp/